The invention relates to a vaporizer, in particular for use in an apparatus for the coating of substrates under vacuum.
In general one understands a process for the vapor deposition or coating to mean the vaporization of at least one material which is present in the form of a target, and indeed for the purpose of condensing this material or these materials, on diverse substrates or products. This process of vapor deposition is carried out under vacuum in order to ensure a controllable and reproducible atmosphere. For the supply of different gases during target vaporization a reaction arises between the vaporized target material and the reactive gases. In this way the most diverse layers can be produced for the improvement of substrate surfaces.
An important component of apparatus of carrying out a substrate coating process of this kind is the so-called vaporizer. This vaporizer must be manufactured so that heat can be led away during the vaporizing on the target material. It is known to mount the target plate for this purpose on a special holder and to directly cool the rear side of the target plate by means of a coolant consisting for example of water. The target plate is thereby fixed on the target holder by screw connections, with this fixation or connection of the target plate with the target holder having to take place in such a way that a penetration of the coolant into the vacuum system can be reliably avoided.
The screw connections used in known vaporizers for the fixation of the target plate are always associated with the disadvantage that the thread space is difficult to evacuate. As screw connections under vacuum can moreover not be lubricated, the danger exists that the screw connections can no longer be released. Finally, with these screw connections it is also disadvantageous that the amount of time required to interchange a target plate is relatively large.
A further disadvantage of known vaporizers lies in the direct cooling of the rear side of the target plate, since the danger exists that the vacuum closure will leak. This occurs in particular with specific target materials, and indeed with frequent change of the target plates also due to wear of the sealing material. Even very small quantities of the coolant liquid entering into the vacuum system can have disastrous effects on the vacuum process. Finally, it can also transpire that on changing the target plate residues of the coolant contaminate the system. Summarizing, it can be noted with respect to customary vaporizers that their direct cooling and screw mounting to a target holder causes grave problems during change of the target plate and also an undesired high expenditure of time.